<!DOCTYPE HTML>
<meta charset=utf-8>
<title>Largest Contentful Paint: Progressively Loaded Image</title>
<body>
  <script src="/resources/testharness.js"></script>
  <script src="/resources/testharnessreport.js"></script>
  <script src="resources/largest-contentful-paint-helpers.js"></script>
  <script src="/common/get-host-info.sub.js"></script>
  <script>
    promise_test(async function (t) {
      assert_implements(window.LargestContentfulPaint, "LargestContentfulPaint is not implemented");
      const beforeLoad = performance.now();
      const observer = new PerformanceObserver(
        t.step_func_done(function(entryList) {
          assert_equals(entryList.getEntries().length, 1);
          const entry = entryList.getEntries()[0];
          const imgElement = document.getElementById('image_id');
          const imageSrc =  imgElement.currentSrc;
          const imageWidth = imgElement.naturalWidth;
          const imageHeight = imgElement.naturalHeight;
          const size = imageWidth * imageHeight;
          const lcpLoadTime = entry.loadTime;
          const lcpRenderTime = entry.renderTime;
          const resLoadTime = calculateResourceLoadTime(imageSrc);
          assert_greater_than_equal(lcpLoadTime,resLoadTime,'Load before LCP event fired');
          assert_greater_than_equal(lcpRenderTime,resLoadTime,'Load before LCP event rendered');
          checkImage(entry, imageSrc, 'image_id', size, beforeLoad);
        })
      );
      observer.observe({type: 'largest-contentful-paint', buffered: true})
    }, 'Ensure Progressive JPEG LCP load and render events occur after resource loading');

    function calculateResourceLoadTime(imageSrc) {
      const entries = performance.getEntriesByName(imageSrc);
      const resourceEntry = entries[0];
      assert_equals(entries.length, 1, 'No Resource timing entry found');
      return resourceEntry.responseEnd;
    }
  </script>
  <img src='/images/computer.jpg?pipe=trickle(982:d1)' id='image_id'/>
</body>
</html>